[Basic evaluation of nitric oxide inhalation therapy].

Abstract

We studied the site of action of nitric oxide (NO) and the dose-response relationship between inhaled NO and PaO2. We also measured nitrosyl-hemoglobin (Hb-NO) levels in arterial and mixed venous blood and NO2 levels in our NO inhalation system to confirm the safety of NO inhalation. In an ovine model of ARDS induced by lung lavage, pressure-flow plots indicated that the site of action of inhaled NO was close to the alveoli. During hypoxia, pulmonary artery pressure decreased as the concentration of inhaled NO increased; PaO2 peaked at 10-20 ppm NO. The levels of Hb-NO in arterial and mixed venous blood during inhalation of 40-60 ppm NO under hypoxic conditions were greater than the levels under normoxic conditions, but Hb-NO still accounted for less than 0.1% of the total Hb. Less than 0.1 ppm on NO2 was generated during inhalation of 5 ppm NO. In conclusion, inhaled NO can dilate pulmonary vessels near alveoli without lowering the O2 carrying capacity of blood. In the present system, only a negligible amount of NO2 was produced.